Connecting a Ping Battery to the Magic Pie

[MonkeyMagic]

The ease of a bike alarm loud like yours is attractive, but I will need another DC to DC converter.  How many amps does that alarm pull?

Hey mate, I have a 6.8Ah 12v lithium battery I run a heap of accessories off. I was going to convert the voltage but that can come at a loss, and the alarm standby would be less than 50mA, and the output alarm current would be MAX 500mAh

So the battery works well. You can also get this battery on eBay haha I've got heaps of stuff from there. Its tiny too I was amazed!!

http://cgi.ebay.com/DC-12V-6800mAh-Pile-Lithium-ion-Rechargeable-Neuf-/110567280754?pt=US_Batteries&hash=item19be52d072

Okay so I'll post the progress

[e-lmer]

Leslie;

Let me know when you get the auto-cutout circuit.

I have been thinking of something like that, but I am stuck
at finding one that won't draw power when the switch is off.

That bistable latching relay may be critical.
Do you know where I can get one?

Elmer

[Bikemad]

That bistable latching relay may be critical.
Do you know where I can get one?

Elmer,

I think Leslie got his relays on eBay:


                Click for more details.               

Alan
 

[MonkeyMagic]

Yes I'm using one of those, I built it into the switch compartment of the GM battery.

Basically I removed the 4 screws of the casing, and de-soldered the key switch and glued the relay in there with the negative connected through the relay.

I switch mine with a wireless key remote it's really convenient! The battery link I posted above is really small, I mounted mine under the battery rack and bolted it on there.

I originally bought 2 of them so I could make switchable series battery circuit for extra power.

They operate on a pulse signal. So 12v negative and positive to turn on, then reverse polarity to turn off. It needs to be pulsed momentarily otherwise it just keeps shorting and will eventually burn out.

[Leslie]

I tried the Relay out today on the HBS and Life Batt and shes a pearler.


To make an easy circuit I just did exactly this and it works very well.




I used a momentary centre off, throw on DPDT toggle switch that reverses the polarity, You should use a 470 ohm 10 watt resistor in case something gets stuck and put the resistor before the DPDT toggle,  so the toggle switch isn't not hooked directly to the battery at 52+v.  The DPDT switch only sees 14v@ 84ma max over a second. Its quite an acceptable circuit in terms of reliability and safety for your gear.

My pack was charging at 58v and I was getting 14v over the coil.  This is fine IMO.  The relay is rated at 1 watt this can produces little more than 1.008 watts of there abouts.

Math for a 48v pack.

470 ohms + 150 ohms = 620 ohms.

I had 58v

So!

58/620 ohms = 0.09355 divider ratio.

V drop over 470 ohm resistor= 470 ohms X 0.09355 = 43.9685v
V drop over the relay = 150 ohm x 0.094 = 14.0325v

That is spot on to what I got on the multimeter rounded off to 5 decimal points.

48v pack at LVC

@ 41v pack/ 620 ohms = 0.06613= divider ratio.

V drop over 470 ohm resistor= 470 ohms X 0.066 = 31.02v

V drop over the relay = 150 ohm x 0.066 = 9.9v



I tested the relay with a 9v batt and it still switches with a nice click..


Cheers.